How Asia's 5,000-year-old rice terraces are inspiring modern flood control

Asia 's 5,000-year-old rice terraces are inspiring modern flood control.

Parks , roofs and riverbanks mimicking the long-used agricultural form are helping Asian cities absorb, hold and purify rainwater.

At Thammasat University , north of Bangkok , tiers of small paddy fields cascade down from the top of the building.

Rice terraces are one of the pillars of Yu 's spongy city theory, which urges cities to turn to soil and greenery not steel or cement to solve flooding and excess rainfall problems.

Yu: Rainwater should be absorbed and retained at the source, slowed down in its flow and then adapted to where it ends up.

"Green" infrastructure can be "a meaningful supplement" to grey infrastructure, says Wang Yuhong , professor of engineering at the Hong Kong Polytechnic University .

The idea could benefit cities with mountains, such as Hong Kong , where rainwater can wash down steep slopes rapidly.

Green infrastructure can show obvious effects in flattening peak flood levels for the types of high rainfall seen once every three to five years.